CN102461077B - Method for discontinuous data transmission in a point-to-multipoint access network, central unit and network terminal unit - Google Patents

Abstract

The invention relates to a method for discontinuously transmitting data (DI1, DI2, DI3) in a point-to-multipoint access network from a central unit to a subscriber-side network termination unit via a distribution network, which connects the central unit with the subscriber-side network termination unit and a plurality of similar further subscriber-side network termination units, in which measures serving for correct data transmission, like Scrambling Codes (SCR) or error correction (FEC), are applied to the data for the single subscriber-side network termination unit before merging with the data for the further subscriber-side network termination units, to a central unit, and to a subscriber-side network termination unit.

Description

Method for discontinuous data transmission in a point-to-multipoint access network, central unit and network terminal unit

technical field

The invention relates to a method according to the preamble of claim 1 for the discontinuous transmission of data in a point-to-multipoint access network via a distribution network from a central unit to a user-side network terminal unit, wherein the distribution network connects the central unit with The subscriber-side network terminal unit, and a plurality of similar other subscriber-side network terminal units; a central unit according to the preamble of claim 3 for having a central unit, a distribution network and a plurality of subscriber-side network terminal units point-to-multipoint access network; relates to a subscriber-side network terminal unit according to the preamble of claim 4 for having a central unit, a distribution network, the subscriber-side network terminal unit and a plurality of similar Point-to-multipoint access network of other user-side network terminal units.

Background technique

In telecommunications, especially in the access area, older point-to-point technologies are increasingly being replaced by point-to-multipoint technologies. In the downstream direction to the end user, the data sent to different end users is time division multiplexed (TDM), while in the upstream direction from the end user, the data from different end users is time division multiple access (TDM) TDMA technology) combination. Thus, data transmissions originating and destined for any end user are discontinuous data transmissions even though the data transmissions are embedded in a continuous data stream on the same medium.

One way to increase the capacity of the point-to-multipoint access network (a radio link can also be identified as such a "network") is to increase the bit rate. From the bit rate range of 144 to 155Mb/s in the 1990s, we are currently dealing with the upcoming 10Gb/s. For point-to-point applications, even bit rates of 100Gb/s are currently being developed.

One problem with this is that as the bit rate increases, the energy consumption of the affected device typically also increases. Energy consumption should be kept low for several reasons:

-Sometimes the device is too far away to work with solar battery support.

- Battery backup operation is expected to be used during periods of power failure.

- Waste heat can interfere.

-Environmental awareness like carbon emissions is playing an increasingly important role.

Contents of the invention

The invention solves this problem by means of the method for discontinuously transmitting data in a point-to-multipoint access network taught in claim 1, the central unit taught in claim 3, and the user-side network terminal unit taught in claim 4 solved.

A basic idea behind the invention is, on the one hand, to deactivate a part of the subscriber network terminal unit, which is adapted to process received data destined for the subscriber network terminal unit, until data is actually expected to be received. Data, on the other hand, is provided so that the subscriber-side network terminal unit operates in such a way that data intended for other subscriber-side network terminal units is not received in advance.

It should be noted that the measures taken to ensure privacy, namely encryption and decryption, are necessary and implemented separately. In US2005/135803A1, as an accompanying measure for encryption and decryption, it is proposed to use error-correcting codes for error detection. Of course, the measures taken for misidentification must also be done individually.

Further embodiments of the invention are found in the dependent claims and the accompanying description.

The invention will be described based on an example in the field of 10Gb/s or 10GPON Gigabit Passive Optical Networks.

Description of drawings

Next, the present invention is described by means of the accompanying drawings:

Figure 1 shows a typical passive optical network in which the method according to the invention can be used.

Figure 2 shows a typical data frame for use in passive optical networks.

Figure 3 shows a simplified block diagram of a central unit of a passive optical network according to the prior art.

Figure 4 shows a corresponding block diagram of the central unit according to the invention.

Fig. 5 shows a simplified block diagram of an optical network termination unit, which is an example of a user-side network termination unit according to the present invention.

detailed description

As shown in FIG. 1, as an example of a point-to-multipoint access network, a typical passive optical network PON is considered in the present invention.

Figure 1 shows a central unit, referred to herein as an optical line terminal OLT, a distribution network DN, and a plurality, here three, of user-side network terminal units, referred to herein as an optical network terminal unit ONT1, ONT2 and ONTn.

The distribution network DN shows a common optical link, not noted here, extending from an optical line terminal OLT to an optical splitter SP, and a plurality of independent optical links, also not noted here, extending from The splitter extends to one of the optical network termination units ONT1, ONT2 and ONTn. Here, devices noted as optical splitters SP are generally passive optical components, acting as splitters in the downlink direction towards end users assigned to optical network termination units ONT1, ONT2 and ONTn, and in the slave In the uplink direction from the end user to the optical line terminal OLT, it acts as a combiner.

It can be clearly seen that each optical network terminal unit ONT1, ONT2 and ONTn receives all data addressed to all optical network terminal units ONT1, ONT2 and ONTn and including other optical network terminal units. Therefore, although only a discontinuous, bursty stream of data is intended for each ONU, it must actually handle a continuous stream of data.

Receiving a continuous stream of data facilitates common transmission technology functions like maintaining synchronicity, error correction, or reducing stability components through scrambling, and is therefore commonly used in legacy applications. Here, as proposed by the invention, the continuous data stream is no longer processed continuously, but only in a bursty manner, however, a remedial measure must be foreseen for such transmission technology functions. Of course, some transmission technical functions like error correction are not absolutely necessary, because these functions only improve data transmission, but do not really endow data transmission capabilities, but other similar synchronization functions are basically necessary.

Figure 2 shows a typical data frame for use in passive optical networks.

This data frame is periodic in nature and a frame length of 125 microseconds is widely used in telecommunications. The frame starts from the frame header FHD, followed by continuous payload parts, each payload part includes a payload header PLH and a payload body PLn, where the payload bodies PL1, PL2, PL3 and PL4 are given. While all payload headers PLH have a fixed length and standardized structure according to the standard or protocol used, the content of the payload body is free and sometimes even variable in length, also according to the standard or protocol used. In the latter case, after the frame header FHD, the remainder of the payload portion from the previous frame can be ended. Unused capacity usually results in stuffing bits or a dummy payload section at the end of the frame. In any case, a continuous bit clock is used for synchronization. There is no systematic distribution between the payload body PLi and the optical network termination unit ONTk.

FIG. 3 illustrates the regulation of data flow similar to that shown in FIG. 2 as is known in the art.

Figure 3 shows three encoders ENC, three channel framing units CFR, one line framing header unit LFRH, one line framing unit LFR, one scrambler unit SCR, one forward error correction unit FEC and the optical Box OL for lines.

Multiple, here three, independent data input streams DI1, DI2 and DI3 pass through the assigned encoder ENC and channel framing unit CFR, and are then forwarded to the line framing unit together with the output data of the line framing header unit LFRH The LFR then transmits the composite signal from the LFR to the optical line OL via the scrambler unit SCR and the forward error correction unit FEC.

A plurality, here three, of independent data input streams DI1, DI2 and DI3 are first encoded in respective encoders, one for each data stream. This ensures privacy because, as mentioned before and shown in Figure 1, each optical network termination unit ONT1, ONT2 and ONTn receives all data destined for all destinations.

The independent data input streams DI1, DI2 and DI3 are considered here as representing the content of one connection or each channel. The content must be transparently sent from this input to the corresponding output of a given Optical Network Termination Unit ONT. Typically, at the output of the optical network terminal unit ONT a single subscriber's terminal or similar is connected, but in principle even another distribution network could be connected.

Any one of the data input streams DI1, DI2 and DI3 may be continuous or discontinuous; even different data streams may be relatively asynchronous with each other. The first step before multiplexing is to unify and synchronize the different data streams. At least before multiplexing, a common data clock is required. To this end, each data input stream DI1, DI2 and DI3 is channel-framed in a separate channel-framing unit CFR after encoding. Here, each data unit of the data input streams DI1 , DI2 and DI3 is processed into a payload header PLH and a payload body PL1 , PL2 , PL3 and PL4 similarly mentioned in the description of FIG. 2 .

In many well-known typical networks, data streams are filled with stuffing bits or dummy data cells to ensure a continuous data stream also for data streams that do not utilize the full provided capacity.

These coded and framed data input streams are input to the line framing unit LFR together with the frame header FHD shown in FIG. 2, where they are usually multiplexed into a common data frame in an asynchronous manner, as shown in FIG. In this network, the capacity of the public link is usually less than the total capacity of the data input streams. Thus, the first stuffing bits or dummy data units from different data input streams are omitted and new stuffing bits or dummy data units are inserted at the end of the frame, or the rest are carried over to the next frame.

In order to improve the quality of data transmission, besides simple framing, many well-known methods can also be used. Two examples given here are scrambling and forward error correction. Other types of error correction or pure error recognition are other examples. These measures imply the opposite action at the receiving side, here the respective Optical Network Termination Units ONT1, ONT2 to ONTn.

Since the latter measures are applied to the framed signal as a whole, their inversion also means that they are applied to the framed signal as a whole, which prevents the processing of those signal parts which belong to the Data flow received by ONT1, ONT2 to ONTn.

In order to solve this problem, according to the present invention, for the data of any data input stream DI1, DI2 and DI3, measures are taken after performing data combination for different optical network terminal units ONT1, ONT2 and ONTn. Therefore, in this The above measures are taken on the data before it is combined with the corresponding data of other data streams. In the given example, this means that scrambling and forward error correction are applied before the data input streams DI1, DI2 and DI3 are combined into a data stream to be sent to the optical line OL.

This forms a corresponding block diagram of the central unit as shown in FIG. 4 .

Figure 4 shows three encoders ENC, three channel framing units CFR, one line framing header unit LFRH, four scrambler units SCR, four forward error correction units FEC, one line framing unit LFR, and a box OL representing an optical line.

The functions performed here are essentially the same as those of the previously mentioned known central unit described on the basis of FIG. 3 . The difference is that, as mentioned above, for the data of any of the data input streams DI1, DI2 and DI3, measures are taken after the combination of data for different optical network terminal units ONT1, ONT2 and ONTn, therefore, in the same data Before the data of the corresponding other data stream is combined, the above-mentioned measures are taken on the data. For inversion, this measure does not need to be taken for other parts of the transmitted signal.

It's worth mentioning here that measures like scrambling or error correction employ some kind of encoding scheme and usually require fixed-length blocks. For this reason, if the payload does not always work with a fixed length, the payload must be filled with padding bits to reach that length. This is only a small disadvantage as the extra load is negligible. This overhead can be reduced by short-run encoding, if acceptable, at the expense of transmission quality.

It is also worth noting that by utilizing hardware for each block individually, hardware for some or all of the blocks, software for each block individually, or software for some or all of the blocks, it is possible to Realize the functions of different blocks in Figure 3 and Figure 4.

Therefore, it is no longer necessary to completely process the transmission signal at each optical network termination unit ONT1, ONT2 to ONTn.

FIG. 5 therefore shows a simplified block diagram of an example of an optical network terminal unit adapted to discontinuously process an incoming data stream in accordance with the present invention.

Figure 5 shows an optical network termination unit ONT comprising a transport function part TFP and a clock CL.

The transport function part TFP is adapted to perform with the forward error correction unit FEC, the scrambler unit SCR, the channel framing unit CFR and the encoder ENC (associated with the optical network terminal unit ONT) processing the data input stream DI1, DI2 or DI3 cooperate. For this purpose, the transport function part TFP may also require information from the line framing header unit LFRH. For this reason, the transport function part TFP needs to be active only when data arrive at its input, and according to the invention it is adapted to be inactive under the control of the clock CL.

The clock CL must be kept synchronized with the time when the transfer function part TFP is inactive, it can disable this part if necessary and reverse the inactive state when data input is expected.

Depending on the protocol and standard used, when establishing a connection to an ONT to make the ONT work, the expected data input time can be fixed, or can be in the frame header or even different payload headers PLH Subsequent reports are reported once per frame.

According to the method of reporting the transmission time to the ONT and its clock CL, the sleep time of the transmission function part TFP can be long or short, and the reduction of energy consumption can be high or low. To guarantee correct operation, it is necessary to be able to wake up in time for resynchronization and rearrangement. However, this is not the main problem.

A similar method of disabling non-continuously used parts of the optical network termination unit ONT can be used for certain parts of the unit for data sent in the opposite direction, here the upstream direction.

Claims (3)

1. A method for the discontinuous transmission of data (DI1) from a central unit (OLT) to user-side network terminal units (ONT1, ONT2, ONTn) via a distribution network (DN) in a point-to-multipoint access network , DI2, DI3), wherein the distributed network connects the central unit (OLT) with the user-side network terminal unit (ONT1, ONT2, ONTn) and multiple similar user-side network terminal units (ONT1, ONT2, ONTn), its characteristics It is that all measures similar to scrambling code (SCR) or error correction (FEC) are performed after combining (LFR) for data (DI1, DI2, DI3) of other user-side network terminal units (ONT1, ONT2, ONTn) , performed separately prior to the merging (LFR), and including measures other than error recognition. 2. Method according to claim 1, characterized in that, in the user-side network termination unit (ONT1, ONT2, ONTn), timing data relevant to the upcoming data transmission is available in advance (CL), and, in The receiving side of the user-side network termination unit (ONT1, ONT2, ONTn) performs at least minimum operations before the upcoming data transmission to prepare for the upcoming data transmission. 3. A central unit (OLT) for a point-to-multipoint access network with a central unit (OLT), a distribution network (DN) and a plurality of user-side network terminal units (ONT1, ONT2, ONTn), characterized by in that said central unit (OLT) comprises a transport function (SCR, FEC) and a multiplexer (LFR), wherein the transport function (SCR, FEC) is adapted for service data transmission, like a scrambling code (SCR) and error correction (FEC), the multiplexer (LFR) is adapted to combine data intended for a particular subscriber-side network termination unit (ONT1, ONT2, ONTn) with data intended for other subscriber-side network termination units (ONT1, ONT2, ONTn ), and said transport function device (SCR, FEC) and said multiplexer (LFR) are arranged in such a sequential manner that firstly the user-side network termination unit (ONT1, ONT2, All transmission functional measures of the data of ONTn), and then merge (LFR) the data for this customer-side network termination unit (ONT1, ONT2, ONTn) with the data for other customer-side network termination units (ONT1, ONT2, ONTn), Also, said transfer function means (SCR, FEC) include means other than means for performing error recognition measures.